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Department Process Engineering

Process Engineering

The research focus of the Process Engineering Department (ENG) ranges from current and future wastewater and drinking water treatment problems, as well as water pollution control and resource reuse. Our long-term goal is to develop sustainable concepts of the water and nutrient cycle in residential areas.

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Payment via mobile, replacement parts made on a 3D-printer, error messages via NFC-tag – Eawag doctoral student Caroline Saul has found some remarkable innovations in companies that market container toilets in developing countries. She sees great potential in making such technologies more widely available. Read more

Ultrafiltration is one of the techniques currently used for disinfecting water – viruses and bacteria are reliably retained by a membrane with extremely small pores. For more than ten years, Eawag has successfully been carrying out research to determine how this method can function using the effect of gravity on water instead of high pressure, cleaning and chemicals. These new discoveries are being applied in increasing numbers of ways. In addition to decentralised drinking water purification, Eawag is now researching uses in areas such as greywater recycling and pre-treatment of seawater for desalination. Read more

MEMBRO3X, a novel combination of a membrane contactor with advanced oxidation (O3/H2O2) for simultaneous micropollutant abatement and bromate minimization

Ozonation is a water treatment process for disinfection and/or micropollutant abatement. However, ozonation of bromide-containing water leads to bromate (BrO3–) formation, a potential human carcinogen. A solution for mitigating BrO3– formation during abatement of micropollutants is to minimize the ozone (O3) concentration. This can be achieved by dosing ozone in numerous small portions throughout a reactor in the presence of H2O2. Under these conditions, O3 is rapidly consumed to form hydroxyl radical (·OH), which will oxidize micropollutants. To achieve this goal, a novel process (“MEMBRO3X”) was developed in which ozone is transferred to the water through the pores of polytetrafluoroethylene (PTFE) hollow fiber membranes. When compared to the conventional peroxone process (O3/H2O2), the MEMBRO3X process shows better performance in terms of micropollutant abatement and bromate minimization for groundwater and surface water treatment. For a groundwater containing 180 μg/L bromide, a 95% abatement of the ozone-resistant probe compound p-chlorobenzoic acid yielded <0.5 μg/L BrO3–, whereas in the conventional peroxone process, 8 μg/L BrO3– was formed. In addition, the efficacy of the MEMBRO3X process was demonstrated with river water and lake water.

Combined partial nitritation–anammox (PN/A) systems are increasingly being employed for sustainable removal of nitrogen from wastewater, but process instabilities present ongoing challenges for practitioners. The goal of this study was to elucidate differences in process stability between PN/A process variations employing two distinct aggregate types: biofilm [in moving bed biofilm reactors (MBBRs)] and suspended growth biomass. Triplicate reactors for each process variation were studied under baseline conditions and in response to a series of transient perturbations. MBBRs displayed elevated NH4+ removal rates relative to those of suspended growth counterparts over six months of unperturbed baseline operation but also exhibited significantly greater variability in performance. Transient perturbations led to strikingly divergent yet reproducible behavior in biofilm versus suspended growth systems. A temperature perturbation prompted a sharp reduction in NH4+ removal rates with no accumulation of NO2– and rapid recovery in MBBRs, compared to a similar reduction in NH4+ removal rates but a high level of accumulation of NO2– in suspended growth reactors. Pulse additions of a nitrification inhibitor (allylthiourea) prompted only moderate declines in performance in suspended growth reactors compared to sharp decreases in NH4+ removal rates in MBBRs. Quantitative fluorescence in situ hybridization demonstrated a significant enrichment of anammox in MBBRs compared to suspended growth reactors, and conversely a proportionally higher AOB abundance in suspended growth reactors. Overall, MBBRs displayed significantly increased susceptibility to transient perturbations employed in this study compared to that of suspended growth counterparts (stability parameter), including significantly longer recovery times (resilience). No significant difference in the maximal impact of perturbations (resistance) was apparent. Taken together, our results suggest that aggregate architecture (biofilm vs suspended growth) in PN/A processes exerts an unexpectedly strong influence on process stability.